Method and system for transmitting/receiving neighbor base-station advertisement message in broadband wireless access system

ABSTRACT

Disclosed is a method and system for transmitting/receiving a neighbor base-station information message in a broadband wireless access system. A base station sets and transmits a neighbor base-station information message, which includes a specific flag field for limiting neighbor base-station information and a reserved field and omits iterative neighbor base-station information depending on a value set in the specific flag field, thereby increasing a transmission efficiency. A mobile terminal receives the neighbor base-station information message from the base station, checks the received message, and then updates an operator ID according to the value set in the specific flag field.

PRIORITY

This application claims the benefit under 35 U.S.C. 119(a) of anapplication entitled “Method And System For Transmitting/ReceivingNeighbor Base-Station Advertisement Message In Broadband Wireless AccessSystem” filed in the Korean Intellectual Property Office on Oct. 26,2004 and assigned Serial No. 2004-85915, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and system fortransmitting/receiving messages in a wireless communication system, andmore particularly to a method and system for transmitting/receivingneighbor base-station advertisement messages broadcast by a base stationin a broadband wireless access (BWA) system.

2. Description of the Related Art

Fourth generation (4G) communication systems, which are the nextgeneration communication systems, are being designed to provide userswith services having various Qualities of Service (QoS) and supporting atransmission speed of about 100 Mbps. Particularly, in current 4Gcommunication systems, research is being undertaken to support ahigh-speed service by ensuring mobility and QoS in broadband wirelessaccess communication systems, such as a local area network (LAN) systemand a metropolitan area network (MAN) system. A representativecommunication system currently being developed is known as an IEEE(Institute of Electrical and Electronics Engineers) 802.16 communicationsystem.

Compared with conventional wireless technologies for providing voiceservices, the IEEE 802.16 communication system enables the transmissionof data in a shorter period of time than needed if using conventionalcommunication technologies, by providing a wider data bandwidth, and canefficiently use channels by sharing all user channels. In addition, theIEEE 802.16 communication system ensures QoS, so that users can receiveservices of different QoS depending on the characteristics of theservices.

From among the IEEE 802.16 communication system, an IEEE 802.16acommunication system does not take into consideration the mobility of aterminal, while an IEEE 802.16e communication system takes intoconsideration the mobility of a terminal (e.g., a mobile station).

Therefore, in the IEEE 802.16e communication system, a base stationperiodically broadcasts a MOB_NBR-ADV (mobile neighbor advertisement)message, which is information about neighbor base stations, to allmobile stations located in a corresponding cell in order to support thehandover of the mobile stations, thereby notifying the mobile stationsof neighbor base-station state information. That is, when a mobilestation located in a cell moves into a neighbor cell, the mobile stationcan perform a handover because the mobile station already understands aneighbor cell's base-station information such as a network identifierand channel characteristics broadcast from the base station.

Table 1 below shows the format of a conventional MOB_NBR-ADV messageused to report neighbor base station information from a base station toa mobile station. These message formats are generally known in the art,so a detailed description thereof will be omitted for the sake ofclarity.

TABLE 1 Syntax Size Notes MOB_NBR-ADV_Message_Format( ) { ManagementMessage Type = 53  8 bits Operator ID 24 bits Unique ID assigned to theoperator Configuration Charge Count  8 bits Incremented each time theinformation for the associated neighbor BS has changed. FragmentationIndex  4 bits This field indicates the current fragmentation index.Total Fragmentation  4 bits This field indicates the total number offragmentations Skip-Optional-Fields Flag  1 bit If set to ‘1’ and if aneighbor has OFDMA PHY the BS-ID for that neighbor is omitted in thismessage. If set to ‘0’, BS-ID is not omitted for any neighbor.N_NEIGHBORS  8 bits For (j=0; j<N_NEIGHBORS; j++){ Length  8 bits Lengthof message information within the iteration of N_NEIGHBOR in bytes. PHYProfile ID  8 bits Aggregated IDs of Co-located FA Indicator, FAConfiguration Indicator, FFT size, Bandwidth, Operation Mode of thestarting subchannelization of a frame, and Channel Number if (FA IndexIndicator = = 1) { FA Index  8 bits This field, Frequency AssignmentIndex, is present only the FA Index Indicator in PHY Profile ID is set.Otherwise, the neighbor BS has the same FA Index or the center frequencyis indicated using the TLV encoded information. } if (BS EIRP Indicator= = 1) { BS EIRP  8 bits Signed Integer from −128 to 127 in units of dBmThis field is present only if the BS EIRP indicator is set in PHYProfile ID. Otherwise, the BS has the same EIRP as the serving BS. }Neighbor BS-ID 24 bits This is an optional field for OFDMA PHY and it isomitted or skipped if Skip Optional Fields Flag = ‘1’ Preamble Index  8bits The index for the PHY profile specific preamble. Preamble Index isPHY specific for SCa and OFDMA. The value of Preamble Index shall beignored and a value of ‘0x00’ shall be used for OFDM PHY HO ProcessOptimization  8 bits HO Process Optimization is provided as part of thismessage is indicative only. HO process requirements may change at timeof actual HO. For each bit location, a value of ‘0’ indicates theassociated reentry management messages shall be required, a value of ‘1’indicates the reentry management message may be omitted. Regardless ofthe HO Process Optimization TLV settings, the Target BS may sendunsolicited SBC-RSP and/or REG- RSP management messages Bit #0: OmitSBC-REQ/RSP management messages during current re-entry processing Bit#1: Omit PKM-REQ/RSP management message during current re-entryprocessing Bit #2: Omit REG-REQ/RSP management during current re-entryprocessing Bit #3: Omit Network Address Acquisition management messagesduring current reentry processing Bit #4: Omit Time of Day Acquisitionmanagement messages during current reentry processing Bit #5: Omit TFTPmanagement messages during current re-entry processing Bit #6: Fullservice and operational state transfer or sharing between Serving BS andTarget BS (ARQ, timers, counters, MAC state machines, etc...) SchedulingService Supported  4 bits Bitmap to indicate if BS supports a particularscheduling service. ‘1’ indicates support, ‘0’ indicates not support:bit 0: Unsolicited Grant Service (UGS) bit 1: Real-time Polling Service(rtPS) bit 2: Non- real-time Polling service (nrtPS) bit 3: Best Effortvalue of ‘1111’ indicates no information on service available  Available Radio Resource  4 bits Percentage of reported averageavailable subchannels and symbols resources per frame 0000: 0% 0001: 20%0010: 40% 0011: 60% 0100: 80% 0101: 100% 0110-1110: reserved 0110-1110:reserved value of ‘1111’ indicates no information on service available Hand Off Neighbor Preference  2 bits 00 Normal 01 Preferred 10 Non-Preferred 11 Reserved DCD Configuration Change Count  4 bits Thisrepresents the Neighbor BS current DCD configuration change count UCDConfiguration Change Count  4 bits This represents the Neighbor BScurrent UCD configuration change count TLV Encoded Neighbor informationVariable TLV specific    }    }

The following Table 2 illustrates information included in a TLV EncodedNeighbor information field of the MOB_NBR-ADV message, which includes adownlink channel descriptor setting (DCD_settings) field and an uplinkchannel descriptor setting (UCD_settings) field.

TABLE 2 Name Type (1 byte) Length (1 byte) Value (Variable-length)DCD_settings Variable The DCD_settings is a compound TLV value thatencapsulates a DCD message that may be transmitted in the advertised BSdownlink channel. This information is intended to enable fastsynchronization of the SS with the advertised BS downlink. The DCDsettings fields shall contain only neighbor's DCD TLV values which aredifferent from the Serving BS corresponding values. For values that arenot included, the MSS shall assume they are identical to the serving BSscorresponding values. UCD_settings Variable The UCD_settings is acompound TLV value that encapsulates a UCD message that may betransmitted in the advertised BS downlink channel. This information isintended to enable fast synchronization of the SS with the advertised BSuplink. The UCD settings fields shall contain only neighbor's UCD TLVvalues which are different from the Serving BS's corresponding values.For values that are not included, the MSS shall assume they areidentical to the serving BS's corresponding values.

The DCD_settings field in Table 2 is configured using the TLV value of aDCD message, which may be expressed in the format of Table 3. Such aDCD_settings field is generally known in the art, so a detaileddescription thereof will be omitted for the sake of clarity.

TABLE 3 Type Name (1 byte) Length Value (variable length) PHY scopeDownlink_Burst_Profile 1 May appear more than once All (see 6.3.2.3.1).The length is the number of bytes in the overall object, includingembedded TLV items BS EIRP 2 2 Signed in units of 1 dBM. All Frameduration 3 4 The number of PSs contained SC in a Burst FDD or TDD frame.Required only for framed downlinks PHY Type 4 1 The PHY Type to be used.SC Power adjustment rule 5 1 0 = Preserve Peak Power SC, SCa 1 =Preserve Mean Power Describes the power adjustment rule when performinga transition from one burst profile to another. Channel Nr 6 1 Downlinkchannel number as SCa, defined in 8.5. Used for OFDM, license-exemptoperation OFDMA only. TTG 7 1 TTG (in PSs) SCa, OFDM, OFDMA RTG 8 1 RTG(in PSs) SCa, OFDM, OFDMA RSSIR,max 9 2 Initial Ranging Max. AllReceived Signal Strength at BS Signed in units of 1 dBm Channel SwitchFrame 10 3 Channel switch frame SCa, Number number as defined in6.3.15.7, OFDM, Used for license-exempt OFDMA operation only Frequency12 4 Downlink center frequency All (kHz). BS ID 13 6 Base Station IDSCa, OFDM, OFDMA Frame Duration Code 14 1 The duration of the frame.OFDM The frame duration code values are specified in Table 230. FrameNumber 15 3 The number of the frame OFDM containing the DCD message.

The conventional base station periodically broadcasts a MOB_NBR-ADVmessage including a TLV encoded neighbor information field as shown inTable 1 in order to notify a mobile station of neighbor base stationinformation. Meanwhile, information related to a base station identifier(BS_ID) field included in the DCD_settings is an iteration ofinformation related to neighbor base-station identifier (neighbor BS_ID)of the MOB_NBR-ADV message. That is, the BS_ID information of theDCD_settings can be recognized by using a neighbor BS_ID and an operatoridentifier of the MOB_NBR-ADV message. Therefore, the conventionalsystem repeatedly transmits the TLV information of the MOB_NBR-ADVmessage corresponding to the number of neighbor base stations, andincurs a signaling load due to iterative transmission of the BS_ID ofthe DCD_settings field.

In addition, an operator identifier (ID) included in the MOB_NBR-ADVmessage in order to report information about a network operator as shownin Table 1 does not change while a mobile station is using the samenetwork operator. Therefore, when operator ID information is included inevery transmitted MOB_NBR-ADV message, overhead may increase, degradingtransmission efficiency.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve theabove-mentioned problems occurring in the prior art, and an object ofthe present invention is to provide a method and system fortransmitting/receiving a neighbor base-station advertisement message tobe transmitted to a mobile station in a broadband wireless accesssystem.

Another object of the present invention is to provide a method andsystem for transmitting/receiving a neighbor base-station message in abroadband wireless access system, capable of omitting an operator ID,which must be transmitted whenever a neighbor base-station advertisementmessage is transmitted, according to necessity and reducing an overheadcaused by iterative transmission of base station identifier information.

To accomplish these objects, in accordance with one aspect of thepresent invention, there is provided a method for receiving a neighborbase-station advertisement message from a base station using a mobilestation communicating with the base station in a broadband wirelessaccess system, the method including receiving a neighbor base-stationadvertisement message, including a predetermined flag field forindicating the presence or absence of operator identifier information;and determining that operator identifier information is current operatoridentifier information when the predetermined flag field indicates theabsence of the operator identifier information is omitted.

In accordance with another aspect of the present invention, there isprovided a method for transmitting a neighbor base-station advertisementmessage from a base station to a mobile station communicating with thebase station in a broadband wireless access system, the method includingsetting a value of a predetermined flag field indicating the presence orabsence of operator identifier information to indicate the absence ofthe operator identifier information; and transmitting a neighborbase-station advertisement message including the predetermined flagfield to the mobile station.

In accordance with still another aspect of the present invention, thereis provided a broadband wireless access system fortransmitting/receiving a neighbor base-station advertisement message,the system including a base station for transmitting a neighborbase-station advertisement message, including a predetermined flag fieldfor indicating the presence or absence of operator identifierinformation; and a mobile station for receiving the neighborbase-station advertisement message and determining whether thepredetermined operator identifier information is current operatoridentifier information when the predetermined flag field that theabsence of the operator identifier information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating the configuration of cells configuredby base stations for supporting an IEEE 802.16e system according to anembodiment of the present invention; and

FIG. 2 is a flowchart illustrating a handover procedure of a mobilestation in a mobile communication system according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription of the embodiments of the present invention, a detaileddescription of known functions and configurations incorporated hereinwill be omitted when it may obscure the subject matter of the presentinvention. It should be noted that the MOB_ADV message will hereinafterrefer to the MOB_ADV message according to an embodiment of the presentinvention unless indicated otherwise.

The present invention proposes a method and system for minimizing thesize of a neighbor base-station advertisement (MOB_NBR-ADV) message tobe transmitted in a broadband wireless access system according to thepresent invention. In detail, the present invention proposes a methodfor omitting an operator identifier(ID) field of the MOB_NBR-ADVmessage, and a method for omitting a base station identifier (BS ID) ofa downlink channel descriptor (DCD) setting field from among atype/length/value (TLV) encoded neighbor information field of theMOB_NBR-ADV message. The following description according to the presentinvention can be applied to the IEEE 802.16e system.

FIG. 1 is a diagram schematically illustrating the configuration of anIEEE 802.16e communication system according to an embodiment of thepresent invention.

A mobile station 10 having received the service of a first base station(BS 1) 21 moves to the cell of a second base station (BS 2) 22 (asdepicted by the arrow), which is a neighbor base station. In this case,the mobile station 10 must have information about the neighbor basestation in advance in order to receive the service of the second basestation 22 and not experience a service discontinuity.

The mobile station 10 can check neighbor base station's network operatorinformation, base station information, scheduling information, availableresource information, whether or not a message is fragmented, etc., byreceiving and using the MOB_NBR-ADV message. The format of theMOB_NBR-ADV message according to the embodiment of the present inventionis shown in Table 4 below.

TABLE 4 Syntax Size Notes MOB_NBR-ADV_Message_Format( ) { ManagementMessage Type = 53  8 bits Operator ID Flag  1 bit If set to ‘1’,Operator ID will be omitted Reserved  2 bits Configuration Change Count 8 bits Incremented each time the information for the associatedneighbor BS has changed. Fragmentation Index  4 bits This fieldindicates the current fragmentation index. Total Fragmentation  4 bitsThis field indicates the total number of fragmentationsSkip-Optional-Fields Flag  1 bit If set to ‘1’ and if a neighbor hasOFDMA PHY the BS-ID for that neighbor is omitted in this message. If setto ‘0’, BS-ID is not omitted for any neighbor. If ( Operator ID Flag = =0)  Operator ID 24 bits Unique ID assigned to the operator } N_NEIGHBORS 8 bits For (j=0; j<N_NEIGHBORS; j++){ Length  8 bits Length of messageinformation within the iteration of N_NEIGHBOR in bytes. PHY Profile ID 8 bits Aggregated IDs of Co-located FA Indicator, FA ConfigurationIndicator, FFT size, Bandwidth, Operation Mode of the startingsubchannelization of a frame, and Channel Number if (FA Index Indicator= = 1) { FA Index  8 bits This field, Frequency Assignment Index, ispresent only the FA Index Indicator in PHY Profile ID is set. Otherwise,the neighbor BS has the same FA Index or the center frequency isindicated using the TLV encoded information. } if (BS EIRP Indicator == 1) { BS EIRP  8 bits Signed Integer from −128 to 127 in units of dBmThis field is present only if the BS EIRP indicator is set in PHYProfile ID. Otherwise, the BS has the same EIRP as the serving BS. }Neighbor BS_ID 24 bits This is an optional field for OFDMA PHY and it isomitted or skipped if Skip Optional Fields Flag = ‘1’ Preamble Index  8bits The index for the PHY profile specific preamble. Preamble Index isPHY specific for SCa and OFDMA. The value of Preamble Index shall beignored and a value of ‘0x00’ shall be used for OFDM PHY HO ProcessOptimization  8 bits HO Process Optimization is provided as part of thismessage is indicative only. HO process requirements may change at timeof actual HO. For each Bit location, a value of ‘0’ indicates theassociated reentry management messages shall be required, a value of ‘1’indicates the reentry management message may be omitted. Regardless ofthe HO Process Optimization TLV settings, the Target BS may sendunsolicited SBC-RSP and/or REG- RSP management messages Bit #0: OmitSBC-REQ/RSP management messages during current re-entry processing Bit#1: Omit PKM-REQ/RSP management message during current re-entryprocessing Bit #2: Omit REG-REQ/RSP management during current re-entryprocessing Bit #3: Omit Network Address Acquisition management messagesduring current reentry processing Bit #4: Omit Time of Day Acquisitionmanagement messages during current reentry processing Bit #5: Omit TFTPmanagement messages during current re-entry processing Bit #6: Fullservice and operational state transfer or sharing between Serving BS andTarget BS (ARQ, timers, counters, MAC state machines, etc...) SchedulingService Supported  4 bits Bitmap to indicate if BS supports a particularscheduling service. ‘1’ indicates support, ‘0’ indicates not support:bit 0: Unsolicited Grant Service (UGS) bit 1: Real-time Polling Service(rtPS) bit 2: Non- real-time Polling service (nrtPS) bit 3: Best Effortvalue of ‘1111’ indicates no information on service available AvailableRadio Resource  4 bits Percentage of reported average availablesubchannels and symbols resources per frame 0000: 0% 0001: 20% 0010: 40%0011: 60% 0100: 80% 0101: 100% 0110-1110: reserved 0110-1110: reservedvalue of ‘1111’ indicates no information on service available Hand OffNeighbor Preference  2 bits 00: Normal; 01: Preferred 10: Non-Preferred; 11: Reserved DCD Configuration Change Count  4 bits Thisrepresents the Neighbor BS current DCD configuration change count UCDConfiguration Change Count  4 bits This represents the Neighbor BScurrent UCD configuration change count TLV Encoded Neighbor informationVariable TLV specific } }

The MOB_NBR-ADV message shown in Table 4 further includes a 2-bitreserved field in order to set the length of the conventionalMOB_NBR-ADV message shown in Table 1 using byte units. In the MOB_NBR-ADV message according to the present invention, an operator ID flagfield is newly defined. The operator ID flag field is used to reportwhether a MOB_NBR-ADV message includes an operator ID field. Forexample, when the operator ID flag field is set to “1”, it indicatesthat the MOB_NBR-ADV message dose not include an operator ID field. Incontrast, when the operator ID flag field is set to “0”, the mobilestation refers to an operator ID field.

Since the operator ID field contains information about a networkoperator, it is unnecessary to periodically update the operator ID fieldwhile a mobile station is using the same operator's network. Therefore,while a mobile station is continuously located in the same operator'snetwork, the operator ID flag field is set to “1” and the operator IDfield can be deleted. As a result, the total size of the MOB_NBR-ADVmessage can be reduced by 3 bytes.

Hereinafter, the other fields of the MOB_NBR-ADV message shown in Table4 will be described.

The MOB_NBR-ADV message includes an 8-bit “Management Message Type=53”field; a “Configuration Change Count” field for representing whether acorresponding message changes, by increasing by “1” wheneverconfiguration changes; a 4-bit “Fragmentation Index” field forrepresenting an order of a currently transmitted message when theMOB_NBR-ADV message is fragmented and therefore transmitted using aplurality of message fragments a 4-bit “Total Fragmentation” field forrepresenting the total number of fragmented messages; and a 1-bit“Skip-Operational-Flag” field. In addition, the MOB_NBR-ADV messageincludes a 24-bit “Operator ID” field when the Operator ID Flag field isset to “0”.

The other fields except for the above-mentioned fields in the Table 4are related to the length, BS ID and handoff of neighbor base stations,which are generally known in the art, so a detailed description thereofwill be omitted for the sake of clarity.

The operation for performing a handover of a mobile station by using theabove-mentioned MOB_NBR-ADV message will be described in detail withreference to the accompanying drawings.

FIG. 2 is a flowchart illustrating a handover procedure of a mobilestation in a mobile communication system according to an embodiment ofthe present invention.

In order to perform a handover, a mobile station 10 must receiveinformation about a neighbor base station in advance of the handoverprocedure by receiving a MOB_NBR-ADV message from a first base station21, from which the mobile station 10 is currently receiving service.Therefore, the first base station 21 communicating with the mobilestation 10 transmits a MOB_NBR-ADV message according to an embodiment ofthe present invention as shown in Table 4 in order to reduce iterativetransmission of the TLV information of a neighbor base-station message.

Then, as shown in FIG. 2, the mobile station 10 receives the MOB_NBR-ADVmessage from the first base station 21 in step 201.

In step 202, the mobile station 10 checks an Operator ID Flag field fromamong the MOB_NBR-ADV message received from the first base station 21.As a result of the determination, if Operator ID Flag field is set to“0”, the mobile station 10 updates the value of the operator ID in step203, and then proceeds to step 204.

Alternatively, in step 202, if it is determined that the Operator IDFlag field is set to “1”, the mobile station 10 directly proceeds tostep 204. In step 204, the mobile station 10 scans a base station 22, towhich the mobile station 10 moves, and then performs a handoverprocedure in step 205.

Meanwhile, the MOB_NBR-ADV message set to reduce iterative transmissionof the TLV information of a neighbor base-station message will bedescribed with reference to Table 4.

The MOB_NBR-ADV message includes a 3-byte “Operator ID” field and a3-byte “Neighbor BS_ID” field. Meanwhile, a 6-byte BS ID field includedin the DCD_setting is created by combination of the 3-byte Operator IDand 3-byte Neighbor BS_ID. Therefore, when the MOB_NBR-ADV messageincludes the Operator ID and Neighbor BS_ID, the 6-byte BS ID field ofthe DCD_setting message can be omitted.

In the prior art, since the TLV information of the MOB_NBR-ADV messagemust be repeatedly transmitted by all neighbor base stations, overheadincreases proportionately to the number of iterative transmissions ofthe 6-byte BS ID of the DCD_setting field. In this case, the BS ID fieldof the DCD_setting TLV has a size of 6 bytes and includes a type of 1byte and a length of 1 byte, so that the total size for representing theBS ID becomes 8 bytes. However, according to an embodiment of thepresent invention, the BS ID field from among the format of theDCD_setting is omitted, thereby reducing overhead “R” as expressed inEquation 1 below.R=N×8 bytes  Equation 1

That is, when a base station broadcasts neighbor base-stationinformation message for 10 neighbor base stations to a mobile station,an overhead of (N×8 bytes=10×8 bytes) 80 bytes can be reduced byomitting the BS ID field included in the DCD_setting message.

As described above, according to the present invention, when a basestation transmits neighbor base station information messages to a mobilestation in a broadband wireless access system, information either notrequired to be repeatedly transmitted for every message or iterativelytransmitted is omitted, and an indication field (Operator ID Flag) forupdating such information is added, so that it is possible to reduceoverhead and improve a transmission efficiency.

While the present invention has been shown and described with referenceto certain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. Accordingly, the scope of the inventionis not to be limited by the above embodiments but by the claims and theequivalents thereof.

1. A method for receiving a neighbor base station advertisement(MOB_NBR-ADV) message by a mobile station in a broadband wireless accesssystem, the method comprising: receiving, by the mobile station, theMOB_NBR-ADV message including an operator identifier (ID) flag fieldindicating a presence or absence of an operator ID field for identifyinga network operator to which the neighbor base station belongs, aConfiguration Change Count field for representing whether aconfiguration of the MOB_NBR-ADV message changes, a Fragmentation Indexfield for representing an order of a currently transmitted message whenthe MOB_NBR-ADV message is fragmented and transmitted using a pluralityof fragmented messages, and a Total Fragmentation field for representinga total number of the plurality of fragmented messages, wherein theoperator ID flag field being set to ‘0’ indicates that the operator IDfield is included in the MOB_NBR-ADV message, and wherein the operatorID flag field being set to ‘1’ indicates that the operator ID field isnot included in the MOB_NBR-ADV message.
 2. The method as claimed inclaim 1, wherein the MOB_NBR-ADV message includes neighbor base stationID information.
 3. The method as claimed in claim 2, wherein when theoperator ID field is included in the MOB_NBR-ADV message, base stationID information is not included in a downlink channel descriptor.
 4. Themethod as claimed in claim 3, wherein the base station ID informationincludes information about a network operator ID and the neighbor basestation ID information.
 5. A method for transmitting a neighbor basestation advertisement (MOB_NBR-ADV) message by a base station in abroadband wireless access system, the method comprising: transmitting,by the base station, the MOB_NBR-ADV message including an operatoridentifier (ID) flag field indicating a presence or absence of anoperator ID field for identifying a network operator to which theneighbor base station belongs, a Configuration Change Count field forrepresenting whether a configuration of the MOB_NBR-ADV message changes,a Fragmentation Index field for representing an order of a currentlytransmitted message when the MOB_NBR-ADV message is fragmented andtransmitted using a plurality of fragmented messages, and a TotalFragmentation field for representing a total number of the plurality offragmented messages, wherein the operator ID flag field being set to ‘0’indicates that the operator ID field is included in the MOB_NBR-ADVmessage, and wherein the operator ID flag field being set to ‘1’indicates that the operator ID field is not included in the MOB_NBR-ADVmessage.
 6. The method as claimed in claim 5, wherein the MOB_NBR-ADVmessage includes neighbor base station ID information.
 7. The method asclaimed in claim 6, wherein when the operator ID field is included inthe MOB_NBR-ADV message, base station ID information is not included ina downlink channel descriptor.
 8. The method as claimed in claim 7,wherein the base station ID information includes information about anetwork operator ID and the neighbor base station ID information.
 9. Abroadband wireless access system for receiving a neighbor base stationadvertisement (MOB_NBR-ADV) message, the system comprising: a mobilestation for receiving the MOB_NBR-ADV message including an operatoridentifier (ID) flag field indicating a presence or absence of anoperator ID field for identifying a network operator to which theneighbor base station belongs, a Configuration Change Count field forrepresenting whether a configuration of the MOB_NBR-ADV message changes,a Fragmentation Index field for representing an order of a currentlytransmitted message when the MOB_NBR-ADV message is fragmented andtransmitted using a plurality of fragmented messages, and a TotalFragmentation field for representing a total number of the plurality offragmented messages, wherein the operator ID flag field being set to ‘0’indicates that the operator ID field is included in the MOB_NBR-ADVmessage, and wherein the operator ID flag field being set to ‘1’indicates that the operator ID field is not included in the MOB_NBR-ADVmessage.
 10. The system as claimed in claim 9, wherein the MOB_NBR-ADVmessage includes neighbor base station ID information.
 11. The system asclaimed in claim 10, wherein when the operator ID field is included inthe MOB_NBR-ADV message, base station ID information is not included ina downlink channel descriptor.
 12. The system as claimed in claim 11,wherein the base station ID information includes information about anetwork operator ID and the neighbor base station ID information.
 13. Abroadband wireless access system for transmitting a neighbor basestation advertisement (MOB_NBR-ADV) message, the system comprising: abase station for transmitting the MOB_NBR-ADV message including anoperator identifier (ID) flag field indicating a presence or absence ofan operator ID field for identifying a network operator to which theneighbor base station belongs, a Configuration Change Count field forrepresenting whether a configuration of the MOB_NBR-ADV message changes,a Fragmentation Index field for representing an order of a currentlytransmitted message when the MOB_NBR-ADV message is fragmented andtransmitted using a plurality of fragmented messages, and a TotalFragmentation field for representing a total number of the plurality offragmented messages, wherein the operator ID flag field being set to ‘0’indicates that the operator ID field is included in the MOB_NBR-ADVmessage, and wherein the operator ID flag field being set to ‘1’indicates that the operator ID field is not included in the MOB_NBR-ADVmessage.
 14. The system as claimed in claim 13, wherein the MOB_NBR-ADVmessage includes neighbor base station ID information.
 15. The system asclaimed in claim 14, wherein when the operator ID field is included inthe MOB_NBR-ADV message, base station ID information is not included ina downlink channel descriptor.
 16. The system as claimed in claim 15,wherein the base station ID information includes information about anetwork operator ID and the neighbor base station ID information.